1. Field of the Invention
The present invention relates to a semiconductor device which is capable of data communication (reception/transmission) through wireless communication and a driving method thereof.
2. Description of the Related Art
In recent days, an individual identification technique using wireless communication (hereinafter referred to as a wireless communication system) has attracted attention. Specifically, RFID tags (also referred to as IC tags, IC chips, RF tags, wireless tags, or electronic tags) have begun to be used for production, management, and the like of individual objects. In addition, the RFID tags are expected to be used for personal authentication.
The wireless communication system is a system in which data communication is performed by wireless communication between a transmitter/receiver serving also as a power supply source or a transmitter/receiver such as a communication device (also referred to as a reader/writer or an interrogator), and a transmitter/receiver such as an RFID tag (hereinafter referred to as an RFID tag).
In many cases, RFID tags are provided with memories in order to be utilized for production, management, and the like of the above-described individual objects. For example, production history can be recorded when the RFID tag is provided with a nonvolatile memory.
As the memories mounted on the RFID tags, there are a mask ROM (MROM), a one time programmable (OTP) memory, a write-once memory, and the like, in addition to the nonvolatile memory.
The OTP memory and the write-once memory are memories which can be written additionally. The OTP memory and the write-once memory have a plurality of memory cells. In addition, the OTP memory and the write-once memory have an advantage in that the memory cells which have been written once cannot be written additionally. That is, data in the memory cells which have been written once is not changed. Thus, the OTP memory and the write-once memory are suitable for applications which need high safety, for example, production control of food, management of medical goods, and the like because data should not be tampered. However, the memory cells which are not written can be written additionally. Therefore, it is possible that information which has been written once is rewritten.
Patent Document 1 is an example of a method for preventing recorded information from being tampered.
In Patent Document 1, an object is to protect data recorded in an IC tag in order to prevent the data from being tampered. The IC tag is provided with a label which is attached on a surface of a base material of an inlet and which can be peeled, a switch which is set so that the switch is damaged when this label is peeled, and a memory in which writing is inhibited when this switch is damaged. Writing to the memory is inhibited when the label of the inlet is peeled. Accordingly, the recorded information can be surely protected at the time of peeling of the label.
Patent Document 1 is effective for preventing data from being tampered, but a procedure is complicated because a damaging process is included; therefore, a place where such a memory is really used might be confused.